1. Field of the Invention
The present invention relates to a communication system and, more particularly, to a communication system capable of switching communication circuits and including a plurality of switching apparatuses which are mutually connected by a plurality of communication circuits and signaling lines (control line) for transfer of call control signals which are provided independently of the communication circuits, wherein during the period of time when two terminals (or telephones) are in the talking state after the setting of the calls has already been completed, the busy circuits between these terminals can be dynamically changed.
2. Description of the Prior Art
An inter-office interface constituted by communication circuits and a signaling link for transfer of call control signals which is provided independently of the communication circuits as mentioned above has been discussed as a common channel signal system in CCITT Recommendation Q. 701-Q. 795, 1984.
In the common channel signal system according to the CCITT Recommendation, with respect to the signaling link for transfer of call control signals, a circuit switching system has been described as a countermeasure when a signaling link failure occurred. However, nothing is considered with regard to the dynamic switching for the communication circuits.